Interventions to Prevent Cognitive Decline and Dementia in Adults without Cognitive Impairment: A Systematic Review

Without preventative strategies, the burden of dementia is likely to increase rapidly worldwide. Primary prevention approaches involve modifying risk factors before symptoms of cognitive impairment develop. This review systematically assesses Randomised Controlled Trials (RCTs) and reviews of RCTs for their effectiveness in primary prevention. We searched Medline, the Cochrane Library, Web of Science and Psych-Info for relevant studies using pre-determined keywords. Both non-pharmacological and pharmacological interventions were considered. Inclusion criteria were sample size greater or equal to 50, at least 6 months of follow-up, and participants with no cognitive impairment at baseline. Outcomes included dementia incidence, cognitive decline and cognitive function. Study quality was rated using the Jadad criteria. Thirty-nine studies, 17 non-pharmacological and 22 pharmacological, were included. Results were heterogeneous across interventions and studies, with few significant effects. Studies investigating physical activity and calcium channel blocker treatment demonstrated significant effects in preventing cognitive decline. There were no conclusive results demonstrating overall capacity of assessed interventions to reduce risk of dementia. The review provides an overview of the current literature, and identifies areas in need of further research.